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            <div><h3 class="title">
                <a name="asio.reference.OperationState"></a><a class="link" href="OperationState.html"
                                                               title="Operation state concept">Operation state
                concept</a>
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    <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span
            class="keyword">class</span> <span class="identifier">O</span><span class="special">&gt;</span>
  <span class="identifier">concept</span> <span class="identifier">operation_state</span> <span class="special">=</span>
    <span class="identifier">destructible</span><span class="special">&lt;</span><span class="identifier">O</span><span
                class="special">&gt;</span> <span class="special">&amp;&amp;</span>
    <span class="identifier">is_object_v</span><span class="special">&lt;</span><span class="identifier">O</span><span
                class="special">&gt;</span> <span class="special">&amp;&amp;</span>
    <span class="identifier">requires</span> <span class="special">(</span><span class="identifier">O</span><span
                class="special">&amp;</span> <span class="identifier">o</span><span class="special">)</span> <span
                class="special">{</span>
      <span class="special">{</span> <span class="identifier">execution</span><span class="special">::</span><span
                class="identifier">start</span><span class="special">(</span><span class="identifier">o</span><span
                class="special">)</span> <span class="special">}</span> <span class="keyword">noexcept</span><span
                class="special">;</span>
    <span class="special">};</span>
</pre>
    <p>
        An object whose type satisfies <code class="computeroutput"><span
            class="identifier">operation_state</span></code>
        represents the state of an asynchronous operation. It is the result of calling
        <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span
                class="identifier">connect</span></code> with a <code class="computeroutput"><span class="identifier">sender</span></code>
        and a <code class="computeroutput"><span class="identifier">receiver</span></code>.
    </p>
    <p>
        <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span
                class="identifier">start</span></code> may be called on an <code class="computeroutput"><span
            class="identifier">operation_state</span></code> object at most once. Once
        <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span
                class="identifier">start</span></code> has been invoked, the caller shall
        ensure that the start of a non-exceptional invocation of one of the receiver's
        completion-signalling operations strongly happens before [intro.multithread]
        the call to the <code class="computeroutput"><span class="identifier">operation_state</span></code>
        destructor.
    </p>
    <p>
        The start of the invocation of <code class="computeroutput"><span class="identifier">execution</span><span
            class="special">::</span><span class="identifier">start</span></code>
        shall strongly happen before [intro.multithread] the invocation of one of
        the three receiver operations.
    </p>
    <p>
        <code class="computeroutput"><span class="identifier">execution</span><span class="special">::</span><span
                class="identifier">start</span></code> may or may not block pending the
        successful transfer of execution to one of the three receiver operations.
    </p>
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            <div class="copyright-footer">Copyright © 2003-2022 Christopher M. Kohlhoff<p>
                Distributed under the Boost Software License, Version 1.0. (See accompanying
                file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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